1. Field of the Invention
The present invention relates to a method for serial data transmission between a position measuring device and a processing unit.
2. Discussion of Related Art
A method, as well as a device for the serial data transmission between a position measuring device and a processing unit is known from DE 100 30 358 A1 of Applicant, which for example allows a highly dynamic regulation of drive mechanisms on the basis of position data generated by the position measuring device. This printed document essentially discloses a suitable protocol structure of a correspondingly laid-out digital interface, by which a rapid, interruptible point-to-point connection between the processing unit and the position measuring device is made possible. Regarding the actual physical layout of such an interface it is merely stated that the proposed protocol structure for the serial data transmission can be performed on the basis of the most varied known interface concepts. But the printed document does not provide details regarding the concrete embodiment of the actual physical structure of the interface.
The same applies to DE 100 30 357 A1 of Applicant, wherein essentially the solution of a problem resulting from the use of the protocol structure from the mentioned DE 100 30 358 A1 is proposed, namely the elimination of a possibly existing chronological uncertainty in regard to position request commands, or recording pulses, which result from the capability of the interface to be interrupted. Such an uncertainty would be particularly disadvantageous in regard to the real time capabilities of the interface, from which result great demands on the position measuring device with respect to the creation, or recording, of position data, which are time-determined as much as possible.
If the principle for serial data transmission known from DE 100 30 358 A1 is to be used in connection with so-called ethernet physics, further problems result because of the required real time capability of the interface. As already mentioned, in the case of a highly dynamic regulation it must be primarily assured that as deterministic as possible a pickup, or recording, of position data by the position measuring device takes place, independent of the time at which a corresponding position request command from the processing unit appears. Possible chronological uncertainties regarding the time of pickup or recording of the position data have a disadvantageous effect on the resultant quality of the regulation. When employing ethernet physics and the basic capability of the interface to be interrupted, real time capability cannot be assured without further measures.